TracheaThe windpipe. Rings of cartilage in its wall keep it open. It divides into two bronchi, one to each lung.
LungsOne on each side of the heart. In them the blood gives up carbon dioxide and takes up oxygen. The right lung is divided into more lobes than the left.
HeartIt lies between the lungs. It pumps blood to them and then to the rest of the body.
DiaphragmA dome-shaped sheet of muscle that separates the chest from the abdomen.
LiverThe large organ just behind the diaphragm. It is deeply cleft into lobes, and in the rat it has no gallbladder.
StomachIt is shaped like half a doughnut. It lies on the rat's left side, against the back of the liver.
SpleenA long, flat organ along the outer curve of the stomach.
Small intestineA long coiled tube in three parts: duodenum, jejunum and ileum. Its coils fill most of the abdomen.
CecumA large blind sac, the first part of the large intestine. Nearly all rodents have a large one.
ColonThe large intestine after the cecum. It ends in the rectum, which opens at the anus.
IncisorsA pair of long, curved, chisel-like teeth in each jaw. They never stop growing, and gnawing keeps them sharp. A rat has no canine teeth.
Vibrissae (whiskers)The long stiff hairs on the snout. They work as feelers.
Submaxillary glandsA pair of large salivary glands on the underside of the neck. The two touch along the midline.
Liver, stomach and kidneys 11
EsophagusThe tube that carries food to the stomach. It passes through the diaphragm and enters the stomach near the middle of its inner curve.
Cardiac partThe left part of the stomach. A thin-walled sac with a tough, smooth lining. It is thought to hold chewed food until it can be digested.
Pyloric partThe right part of the stomach. Its wall is thicker, and its folded lining holds the glands that make gastric juice. It narrows to the pylorus.
DuodenumThe first part of the small intestine. It is a U-shaped loop on the rat's right side.
PancreasNot one solid organ in the rat. It is a gland scattered in small lobes through the sheet of tissue that holds the duodenum.
Bile ductCarries bile from the lobes of the liver straight to the duodenum. A rat has no gallbladder to store the bile on the way.
Median lobeThe lobe in the middle, in front of the others. It lies against the diaphragm. A cleft partly divides it in two.
Left lobeA large lobe on the rat's left, behind the median lobe. Its back rests against the stomach.
Right lobeThe lobe on the rat's right. It is partly divided into a front part and a rear part. The right kidney fits against it.
Caudate lobeA small lobe in two parts that fits round the esophagus. It lies against the inner curve of the stomach. It is also called the Spigelian lobe.
KidneysBean-shaped organs on the back wall of the abdomen. The right kidney lies farther forward than the left.
How this list was compiled: Every name checked on 2026-09-30 in two sources on the rat. H. R. Hunt, A Laboratory Manual of the Anatomy of the Rat (1924, public domain): whiskers, incisors, salivary glands, chest organs, the lobes of the liver, the missing gallbladder, the two regions of the stomach, the intestines and the kidneys, https://archive.org/details/laboratorymanual00hunt. H. N. Martin and W. A. Moale, Handbook of Vertebrate Dissection, part 3, How to Dissect a Rodent (1884, public domain): the same organs in the brown rat, https://archive.org/details/ahandbookverteb01moalgoog. E. C. Greene, Anatomy of the Rat (1935), searched inside on the Internet Archive, for the liver lobes, the missing gallbladder, the diffuse pancreas and the parts of the stomach, https://archive.org/details/anatomyofrat0000euni. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
A rat diagram labeled in two views. The first shows the whole rat on its back, opened. The second spreads the four lobes of the liver and shows the stomach, duodenum and kidneys. It is a plan, not to scale.
Read the full guide
Whole rat
The rat lies on its back with its head to the left, so its left side is at the top. From the front: trachea, heart and lungs, diaphragm, liver, stomach and spleen, the coiled small intestine, the large cecum and the colon. The long front teeth are the incisors.
Liver and stomach
Switch to Liver and stomach for a rat digestive system diagram up close. The liver has four lobes and no gallbladder, so the bile duct runs straight to the duodenum. The stomach has a thin-walled cardiac part and a thicker pyloric part. Press Quiz me and the page becomes a rat anatomy quiz.
Looking for the gallbladder? A rat has none, though a mouse does.
Questions and answers
Do rats have a gallbladder?
No. A rat's liver has no gallbladder to store bile. The bile runs from the lobes of the liver through the bile duct straight into the duodenum.
How many lobes does a rat's liver have?
Four: the median lobe, the left lobe, the right lobe and the small caudate lobe. The median and right lobes are each partly divided in two, so a count of lobes and lobules comes out higher.
Why do a rat's front teeth keep growing?
The incisors of rodents grow all through life. Hard enamel covers only the front of each tooth, so gnawing wears the softer back away faster and leaves a sharp, chisel-like edge.
What is the cecum in a rat?
A large blind sac at the start of the large intestine, where the small intestine joins it. Nearly all rodents have a large cecum.